Patterns and Distributions of Urban Expansion in Global Watersheds. Issue 8 (19th August 2021)

• Record Type: Journal Article
• Authors: Huang, Qingxu; Zhang, Han; van Vliet, Jasper; Ren, Qiang; Wang, Raymond Yu; Du, Shiqiang; Liu, Zhifeng; He, Chunyang
• Is Part Of: Earth's future. Volume 9:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-19
• Subjects: urbanization -- basin -- urban sustainability -- urbanizing watershed -- watershed management; Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2021EF002062
• Languages: English
• ISSNs: 2328-4277

Abstract

Abstract: Understanding urban expansion at the watershed scale is important because watersheds are important carriers of ecological and environmental impacts. However, current analyses are mainly restricted to administrative units only. Here, we used a long‐term multitemporal data set of urban land to quantify the spatiotemporal trends in the extent and form of urban expansion from 1992 to 2016 in endorheic and exoreic watersheds, globally. Overall, urban expansion in 70% of watersheds (154/220) showed a decelerating trend. The average urban expansion speed of these watersheds in the last 6 years was approximately half of that in the last 24 years. Urban expansion speed in endorheic watersheds lagged behind the counterparts in exoreic watersheds, with the former approximately 1/4 of the latter. More importantly, the pattern of urban expansion in endorheic watersheds was following the low‐density and sprawling trend in exoreic watersheds, which could exert far‐reaching impacts on the sustainability of endorheic watersheds located in arid lands. These findings suggest the need to look beyond administrative city boundaries for land use planning and policies in the context of watershed management. Plain Language Summary: Urban expansion and its impacts are not restricted in urban boundary, but manifest at broader scales, such as watersheds. Previous studies mainly examine the characteristics of urban expansion from the perspective of administrative division, while a comprehensive understanding of the watershed scale is lacking. This study investigated five features of urban expansion (speed, trend, heterogeneity, mode, and efficiency) among thousands of watersheds globally, and compared these features between endorheic and exoreic watersheds. The results show that, globally, urban expansion slowed down in most of the watersheds. However, the unevenness and low‐density development of urban land still dominated in both endorheic and exoreic watersheds. This study could provide a benchmark and proxy for measuring human activities and their environmental impacts at the watershed scale. It also calls for a governance shift from administrative boundary to watershed boundary. Key Points: We quantify five features of urban expansion among 220 watersheds globally for the last 25 years Most of the watersheds globally experienced a decelerating and sprawling urban expansion Rapid and low‐density of urban expansion in endorheic watersheds may threaten their sustainability